A device in which a touch panel is attached to the surface of a liquid crystal panel is known as a display device with a touch input function (see Patent Document 1). To increase mechanical strength, a device in which a cover glass is disposed on the surface of a touch panel is known. However, to make the device thinner and lighter, a device in which a touch sensor is formed on the surface of a substrate made of a tempered glass (referred to as tempered glass substrate below), and in which the cover glass is eliminated has also been proposed (see Patent Document 2).